Revert "Make RelativePath use abspath rather than realpath for the 'path' variable."

This reverts commit 121d89dfcd4f6ebe1c89524b3f9ca11ddd437e77.

R=dpranke@chromium.org

> Make RelativePath use abspath rather than realpath for the 'path' variable.
> This allows gyp to work correctly in symlink-heavy environments. Basically,
> this is because gyp paths need to be in a consistent tree, so we need to
> compute a path to the target within the *stated* tree, even if it is not
> the real underlying path to the target. The 'relative_path' variable does
> need to be resolved using realpath, since gyp or the underlying build system
> might cd to it before looking for the 'path' target.
>
> Also make Ninja's host configuration consult environment variables analogous
> to those it previously had for the target configuration, and replace os.getenv
> with os.environ.get for consistency.
>
> R=thakis@chromium.org

BUG=

Review URL: https://codereview.chromium.org/1315373003 .
5 files changed